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Geotechnical Earthquake
Engineering
by
Dr. Deepankar Choudhury Humboldt Fellow, JSPS Fellow, BOYSCAST Fellow
Professor
Department of Civil Engineering
IIT Bombay, Powai, Mumbai 400 076, India.
Email: dc@civil.iitb.ac.in
URL: http://www.civil.iitb.ac.in/~dc/
Lecture – 34
IIT Bombay, DC 2
Module – 8
Site Response Analysis
Example # 1
Case Study
on
Seismic Ground Response Analysis
for Mumbai, India
D. Choudhury, IIT Bombay, India
Ref.: V. S. Phanikanth, Deepankar Choudhury and G. R. Reddy
(2011); "Equivalent-linear seismic ground response analysis of
some typical sites in Mumbai", Geotechnical and Geological
Engineering, Springer, Vol. 29(6), 1109-1126.
4
EQUIVALENT LINEAR GROUND
RESPONSE ANALYSIS FOR MUMBAI
Mangalwadi site near Girgaon (MBH#1, MBH#2);
Walkeswar site (WBH#1, WBH#2) ; and
BJ Marg near Pandhari Chawl site (BBH#1, BBH#2
& BBH#3)
Equivalent-linear Ground response Analysis for some
typical Mumbai Soil sites:
D. Choudhury, IIT Bombay, India
Typical bore hole data at soil site MBH#1 at Mumbai [Phanikanth et al. 2011, Geotech. and Geological Engg., Springer]
D. Choudhury, IIT Bombay, India
Acceleration-time history of
4 different input motions [Phanikanth et al. 2011, Geotech.
and Geological Engg., Springer]
D. Choudhury, IIT Bombay, India
Output Acceleration-time history at GL for soil site MBH#1 at
Mumbai when input was 2001 Bhuj motion
[Phanikanth et al. 2011, Geotech. and Geological Engg., Springer]
Software used, DEEPSOIL v3.5beta (2008)
D. Choudhury, IIT Bombay, India
Acceleration response spectra at ground level with 5% damping for
soil site MBH#1 at Mumbai under various earthquake motions [Phanikanth et al. 2011, Geotech. and Geological Engg., Springer]
D. Choudhury, IIT Bombay, India
Typical soil amplification for earthquake acceleration at various
soil sites in Mumbai under different earthquake motions [Phanikanth et al. 2011, Geotech. and Geological Engg., Springer]
D. Choudhury, IIT Bombay, India
Acceleration Response Spectra for site MBH#1 at various layers
for input motions (a) Bhuj 2001 (b) Loma Prieta 1989 (c) Loma
Gillory 1989 (d) Kobe 1995 [Phanikanth et al. 2011, Geotech. and Geological Engg., Springer]
D. Choudhury, IIT Bombay, India
Comparison of frequencies and validation of model for
ground response analysis in Mumbai subjected to 2001 Bhuj motion
[Phanikanth, 2011, Ph.D. Thesis., IIT Bombay]
D. Choudhury, IIT Bombay, India
Seismic Zonation Map of India as per BIS 1962 and 1966
D. Choudhury, IIT Bombay, India
Seismic Zonation Map of India as per BIS 1970 and 1984
D. Choudhury, IIT Bombay, India
Seismic zonation map of India [as per IS 1893 – Part 1 (2002)]
with highlight on Soil Characterization
• Only 3 types of soil!!!
Soft soil
Medium soil
Hard rock
• Characterization of Soil Based
on SPT ‘N’ Value, irrespective of
soil type !!
• No DYNAMICS (for soil
characterization) is involved!!!
Soil Classification for Seismic Design in USA (NEHRP-2003)
Choudhury (2010) in Structural Longivity, 3(2), 155-170.
Dr. Deepankar Choudhury, IIT Bombay
Soil Classification as per Eurocode 8 (2004)
Dr. Deepankar Choudhury, IIT Bombay
Comparison of Soil Classification as per
Modern Seismic Codes Worldwide
Dr. Deepankar Choudhury, IIT Bombay
Soil Amplification Factor for various control Periods
for different subsoil class for
Earthquake Type 1 (Ms > 5.5) as per Eurocode 8
Soil Amplification Factor for various control Periods
for different subsoil class for
Earthquake Type 2 (Ms < 5.5) as per Eurocode 8
Example # 2
Case Study
on
Seismic Ground Response Analysis
for Four Ports in Gujarat, India
D. Choudhury, IIT Bombay, India
Ref.: Jaykumar Shukla and Deepankar Choudhury (2012); "Seismic
hazard and site-specific ground motion for typical ports of Gujarat",
Natural Hazards, Springer, Vol. 60(2), 541-565.
Location of selected
Ports in Gujarat, India
7/11/2013
67, E 68, E 69, E 70, E 71, E 72, E 73, E 74, E 75, E
19, N
20, N
21, N
22, N
23, N
24, N
25, N
26, N
F18
F17
F14 F15
F13
F12 F25A F5
F2
F1
F4
F3F6
F7
F8
F10
F9
F33
F35
F34
F37
F38 F42
F41
F43
F45 F46
F31
F32
F24
F49F23
F48
F24
F26
F21
F28
F29
F30
Kandla port site
Mundra port site
Hazira port site
Dahej port site
Fn Fault line
Legend
0 N
Shukla and Choudhury (2012) in Natural Hazards, 60(2), 541-565.
Uniform Hazard Spectra for
Kandla and Mundra port sites
• UHS obtained are for rock sites
• Compared with of IS:1893 -Part 1 (2002)
specified spectra for rock sites – MCE Spectra
• As per IS:1893 – Part I (2002), Design Basis
Earthquake can be taken as 50% of MCE.
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
0.0
0.5
1.0
1.5
2.0
2.5
Retrun Period 2475 years
Retrun Period 475 years
Retrun Period 72 years
IS 1893 (2002)- Zone V
Sp
ectr
al A
ccel
erat
ion
(g
)
Spectral Period (s)
Kandla Port Site
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
0.0
0.5
1.0
1.5
2.0
Sp
ectr
al A
ccel
erat
ion
(g
)
Spectral Period (s)
Mundra Port Site
Retrun Period 2475 years
Retrun Period 475 years
Retrun Period 72 years
IS 1893 (2002)- Zone V
Shukla and Choudhury (2012) in Natural Hazards, 60(2), 541-565.
Stiff Clay
Typical Geotechnical Characterization
0 200 400 600 800 1000 1200
25
20
15
10
5
0
200 400 600 800
40
35
30
25
20
15
10
5
0
Average (used in present study) Imai, 1977 (for all soils) Jinan, 1987 (for all soils)
Imai and Yoshimura, 1970 (for all soils)) Imai and Tonouchi, 1982 (for all soils) Iyisan (for all soils)
Jafari et al., 1997 (for all soils) Yokota et al., 1991 (for all soils) Seed and Idriss, 1981 (for all soils)
Athanasopoulos, 1995 (for all soils) Kiku, 2001 (for all soils)
Dep
th (
m)
Shear Wave Velocity (m/sec)
Kandla Port siteB
Mundra Port site
Dep
th (
m)
Shear Wave Velocity (m/sec)
Silty Clay
Stiff Clay
Silty Sand
Stiff Clay
Sandy
Gravel
Silty Sand
Dense
SiltySand
Shear wave velocities are estimated from 10
empirical correlations and then averaged.
0 20 40 60 80
40
35
30
25
20
15
10
5
0
0 20 40 60 80 100
Mundra port site
Dep
th (
m)
SPT N-Value
Borehole 1
Borehole 2
Kandla port site A
Borehole 1
Borehole 2
Site characterization from available
geotechnical investigations
Shukla and Choudhury (2012) ASCE GSP No. 225, 1650-1659.
Typical synthetic time
history for Kandla Port
0 10 20 30 40 50 60 70 80 90 100
-0.8
-0.4
0.0
0.4
0.8
Spec
tral
Acc
eler
atio
ns (g
)
Time (sec)
Bhuj Earthquake 2001 (recorded at Ahemedand passport office, N-W component)
Level 3 ground motion(2475 years return period)
Level 2 ground motion(475 years return period)
Level 1ground motion(72 years return period)
Kandla Port
Shukla and Choudhury (2012) in Natural Hazards, 60(2), 541-565.
Ground Response Analysis
0.01 0.1 1 10
0.1
1
10
Pse
ud
o-
Acc
eler
atio
n (
g)
Period (sec)
Layer 1, Damping: 5.0%
Layer 2, Damping: 5.0%
Layer 3, Damping: 5.0%
Layer 4, Damping: 5.0%
Kandla Port - Level 3 ground motions
0.1 1 10
0.0
0.5
1.0
1.5
2.0
2.5
Kandla Port - Level 3 ground motions
Am
pli
fica
tio
n r
atio
Frequency(Hz)
Layer 1 to Bedrock
Layer 2 to Bedrock
Layer 3 to Bedrock
Layer 4 to Bedrock
Layer
NO
Avera
ge
SPT-
value
Description Modulus reduction
curve and damping
curve selected
1 10 Soft clay Sun et al. (1988)
2 17 Stiff clay Vucetic and Dobry
(1991)
3 35-40 Medium silty
sand
Idriss (1990), upper
range
4 50 Stiff to very stiff
clay
Vucetic and Dobry
(1991)
• Ground Response analysis is carried out using
equivalent liner model using SHAKE91 (Schnabel et al.,
1972).
• Modulus reduction curves and damping curves are
selected based on the Soil properties
• Typical results in form of Pseudo-acceleration response
spectra and transfer function (amplification factor)
Shukla and Choudhury (2012) in Natural Hazards, 60(2), 541-565.
Important observations Contributing faults:
• Kandla port :F13, F25A, F14 ; Mundra port:F25A and F13 ; Dahej port : F33 and
F30; Hazira port : F34
• IS:1893 part 1:2002, underestimates the seismic ground motions for the two port sites
of Kachchh region however for Dahej and Hazira ports they are in agreement.
Ground
Motion
level
Peak ground accelerations (g) IS:1893
Part 1 (2002 )
Mundra
port site
Kandla
port site
Hazira
port site
Dahej
port site
Zone V Zone III
Level 1 0.07 0.12 0.05 0.04 ---
Level 2 0.19 0.25 0.10 0.10 0.18 0.08
Level 3 0.33 0.40 0.17 0.18 0.36 0.16
Peak ground accelerations obtained for port sites
IIT Bombay, DC 26
End of
Module – 8
IIT Bombay, DC 27
Module – 9
Seismic Analysis and
Design of Various
Geotechnical Structures
IIT Bombay, DC 28
Seismic Design of
Retaining Wall
Introduction
Retaining walls
› are built for the purpose of holding back earth which would
otherwise move downwards.
› knowledge of seismic earth pressure is very important for
design of retaining structures in the earthquake prone areas.
D. Choudhury, IIT Bombay, India 29
Typical Retaining wall sections commonly used in practice (Source:http://www.stonescapecontracting.com/images/images/walls/Retaining_Walll_Type_Function_lg.jpg)
Earth Pressures on Retaining Walls
D. Choudhury, IIT Bombay, India 30
Earth pressures-
› at rest earth pressure
› active earth pressure
› passive earth pressure
Earth pressure conditions
Failure of Retaining Walls
D. Choudhury, IIT Bombay, India 31
Failure of gravity retaining wall
(Source: http://www.geofffox.com) (Source: http://www.parmeleegeology.com/)
Retaining walls may fail during an earthquake, if they are not
designed to resist additional destabilizing earthquake forces.
Seismic Analysis and Design of Retaining Walls
Seismic analysis/design of retaining walls mainly consists of
› Determining magnitude of additional destabilizing forces that act
during an earthquake
› Determining seismic active and passive earth pressures due to all
destabilizing forces (static + seismic)
› Design section based on above parameters using
1. Force based approach
2. Displacement based approach – for performance based
design
D. Choudhury, IIT Bombay, India 32
Pseudo-static Method
33
Theoretical background of seismic coefficient lies in the
application of D´Alembert´s principle of mechanics.
Example of elementary seismic
slope stability analysis
(Towahata, 2008)
D’Alembert’s principle of
mechanics
Towhata, I., (2008), Geotechnical Earthquake Engineering, Springer,
Tokyo, Japan.
D. Choudhury, IIT Bombay, India
Conventional Seismic Design of Retaining Walls
Pseudo-Static Approach Proposed by Mononobe-Okabe (1929)
Questions: Value of kh and kv to be used for design?
Soil amplification?
Variation of seismic acceleration with depth and time?
Effect of dynamic soil properties? etc.
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